The invention relates to a device for actuating a hydrostatic drive with a periodically operable switch valve which connects a resonant pipe connected to the hydrostatic drive for the generating of standing pressure waves in the hydraulic fluid under resonant conditions alternately to a pressure supply line and a return line.
In order to avoid the disadvantages of throttle-controlled hydrostatic drives, particularly the throttle losses, it is known to connect the drive not continuously via a throttle valve but periodically to a hydraulic fluid supply line or a return line, namely via switch valves, to each of which a non-return valve is connected in parallel. The opening of the switch valve in the hydraulic fluid supply line causes an accelerating of the drive, the inertia of which upon the closing of this switch valve leads to a reduction in the pressure of the compressible hydraulic fluid in the drive range to a pressure which is less than the closing pressure of the non-return valve in the region of the return line, so that hydraulic fluid can be drawn in via the return line until the switch valve in the supply line again opens and the process is repeated. In the case of a regenerative braking of the drive, there is obtained, upon the closing of the switch valve in the return line, an increase in the pressure of the drive-side hydraulic fluid to an amount exceeding the closing pressure of the non-return valve in the region of the supply line, which results in a pumping of the hydraulic fluid back into the supply line. This additional flow of hydraulic fluid caused by the pulsed actuation of the drive causes a corresponding recovery of energy and thus an improved efficiency which, to be sure, is obtained at the cost of a comparatively small dynamics and a corresponding structural expense.
If the development of standing pressure waves in the hydraulic fluid under resonant conditions is assured in a resonant pipe connected in front of a hydrostatic drive in the manner that the resonant pipe is connected via a switch valve actuated with a corresponding resonant frequency alternately to a hydraulic fluid supply line and a return line, then, with such pulsed actuations there is obtained a simple storing of energy during the pressure-pulse pauses, as has been shown by fundamental examinations. To be sure, these known examinations still do not provide any solution for the technical use of this resonant pipe upon the pulsed actuation of hydrostatic drives since, with the operating path of these drives, the resonant conditions for the development of the standing pressure waves change and therefore the resonant conditions cannot be maintained.